In Canada, lightning flashes occur about 2.34 million times a year; with the highest levels of concentration during the summer months.
While most lightning on earth is ground-to-cloud, recent research has identified that the majority of lightning events to tall structures, such as wind turbines, occur in the presents of ground-to-cloud leaders – upward lightning. More importantly, the majority of ground-to-cloud leaders transpire following a sudden change in electric field initiated by either cloud-to-cloud, cloud-to-air or cloud-to-ground discharges.
Since the late 1990’s, the utility grade wind turbine sector has identified lightening events as a significant risk factor. Today, many standards and guidelines (such as IEC 61400-24:2010) exist; however, the majority of lightning-protection-system standards and guidelines utilized by the wind turbine industry do not address upward moving lightning.